First Term
: This is the definition of the first term.
Second Term
: This is one definition of the second term.
: This is another definition of the second term.
To expand upon @maartin 's list, here is a list of many of the common implementations to have extended Markdown to include Definition Lists, with a link to their docs
Even though W3C decided to change their name to Term-Description Groups in HTML5, Definition Lists are a commonly used extension. The discussion on CommonMark above has been looking at implementing this since 2014, and they are only holding back in case some implementations find the ‘back-tracking’ hard to implement. GitLab are looking at it already, and once CommonMark adopts it the people like Github who follow CommonMark will do the same, so it’s only a matter of time.
It would be great to add Obsidian to the list of software that supports it - is the feature already available in any of the parsing libraries Obsidian uses?